The present invention relates to a film advancing mechanism for cameras, more precisely relates to a film advancing mechanism, which is capable of advancing and rewinding a film.
In conventional cameras, a film advancing mechanism includes a spool, which is rotatably supported in a camera proper, having a spool-gear. A driving motor has an output shaft, a motor-gear is fixed to the output shaft, and a reduction gear unit is communicated with the motor-gear. The reduction gear unit has a transmitting gear, and a sun gear of a swing gear unit or a clutch unit is engaged with the transmitting gear. The swing gear unit has a swing arm, which is capable of swinging about a shaft, said sun gear, which is provided on the swing arm and capable of rotating about the shaft, and a switching gear, which is provided to a front end section of the swing arm and engaged with the sun gear. The switching gear is capable of selectively engaging with an advancing gear for advancing a film and a rewinding gear for rewinding the film on the basis of positions of the swing arm.
When the driving motor rotates the output shaft in the normal direction, driving force is transmitted to the sun gear via the transmitting gear, so that the swing arm is swung toward the spool-gear. Then the switching gear is engaged with the advancing gear, so that a film is advanced and wound around the spool. On the other hand, when the driving motor rotates the output shaft in the reverse direction, the swing arm is swung in the opposite direction. Then the switching gear is engaged with the rewinding gear, so that the film is rewound.
These days cameras have become smaller and smaller, so the film advancing mechanism assembled for cameras is also required to be smaller.
In the conventional film advancing mechanism, the reduction gear unit includes a multiple reduction gears, so that the unit must be large and has a complex structure. Having the large and complex structure, the mechanism or camera having the same must be expensive.
The size of the film advancing mechanism depends on sizes of reduction gears in the reduction gear unit. It is possible to employ hard metal gears but using such gears with higher accuracy will raise manufacturing cost of the mechanism.
Further, metal gears cause a tremendous noise while advancing and rewinding a film.